A large chunk of ice that has built up in the back of my Sub Zero Model 561 on the refrigerator side. A repairman came and said that I need to replace the defrost heater, defrost timer, and the defrost thermostat to the tune of almost $500. His only diagnostic test was to open the door and look at the ice. He did not have the parts in stock and I have not yet given him the go ahead to make the repair.

Should the repairman have made any actual tests to diagnose the problem?
Is it likely that all these parts need to be replaced?
Should I just defrost the unit manually and see if the build up comes back?

Yes, how could he know if the heater or thermostat was bad if the timer was bad? Do you know what the timer motor looks like?

No, I do not know what the timer motor looks like.

Small black plastic box about 2" square. Will have several wires going to it. Will have a slot where you can insert a screwdriver. Can turn only one way. I am guessing you have a side by side model. I have freezer below with compressor above so I don't know where it will be but will be located in the compressor compartment. Locate timer motor and turn 1/4 turn. If defrost heater melts ice, replace timer motor. Timer will probably get stuck again. Do this once each day until you can replace timer motor.

Let me know when you have found timer motor.

Thanks for your help. I located the timer motor and turned it 1/4 turn. The ice is still there, but it seems to have melted a little bit. There is some moisture on the wall below the ice. Also the timer is still turning. I will monitor it over the next several days.

Moisture on the wall indicates defrosting. Defrosting indicates that heater and thermostat are functioning. A blow drier will of course remove the ice. Monitor the timer but it is likely to malfunction again. As I am sure you can see, replacement of the timer is quite simple.

Harold,
I am going to clean out the ice build up and replace the timer. Your knowledge has saved me hundreds of dollars. I have crossed that repairman off my list and will never call them again. Thanks so much for your assistance.

Did replacing the timer solve your ice build-up problem?